Bacterial cells and more particularly, bacterial spores, are able to survive in relatively adverse environments. The surface membranes of these organisms provide protection against harmful conditions. However, the surface membrane of a bacterial cell or spore comprises a shell protecting the deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) contained therein that makes this material almost inaccessible for purposes of analysis and study. While it is possible to break down the surface membrane to expose the RNA and DNA of the spore with heat or by using chemical lysing agents, these techniques denature the cell-nuclear material so that the material is not of much use for analysis.
Examples of prior art techniques used for disrupting the surface membrane of bacteria cells (but not bacterial spores) include the use of a pulsed high voltage that creates a high voltage electric field. This electric field is capable of breaking down a bacterial cell wall, but has little effect on the surface membrane of bacterial spores. In a paper entitled, "Destruction of Living Cells by Pulsed High-Voltage Application," IEEE Transactions on Industry Applications, 24:3: May/June 1988, 387-394, Akira Mizuno and Yuji Hori report on the destruction of yeast cells (Saccharomyces cerevisiae) in a water solution using a high voltage pulse applied to electrodes exposed to the solution. The experiment was done with ionized water, and with a 1-3 percent NaCl solution in which the yeast cells were dispersed at a concentration of about 10.sup.7 cells/cm.sup.3. High voltage pulses were applied to the solution N times (e.g., where N equals 175 times), and the pulses had a peak of either 12 kV or 20 kV, and a pulse width of about 90 to 160 .mu.s. The survivability of the yeast cells decreased with increasing N. The high voltage pulse visibly destroyed some of the cells by puncturing their surface membranes, and destroyed others without any visible damage. The authors also postulate that some of the cells were destroyed by the shock wave resulting from application of the high voltage pulse to the solution. However, it appears that although many cells are killed using the high voltage pulse, and that some cell surface membranes are ruptured, the process does not assure that even a majority of the cell membranes will be punctured, exposing the DNA and RNA within the cells.
In a paper entitled, "Effects of High Electric Fields on Microorganisms," Bicochim. Biophys. Acta, 148, (1967), 789-800, W. A. Hamilton and J. H. Sale report on the effects of a series of high voltage direct current (DC) pulses of up to 30 kV/cm. on the membranes of Escheria coli, Staphylococcus aureus, Bacillus cereus, Bacillus polymyxa and other bacterial cells suspended in a 0.1 percent NaCl solution. It was noted by the authors of this paper that when E. coli were subjected to the DC pulse treatment, ninhydrin-positive material and 260-m.mu. absorbing material were found in the medium. Since amino acids, purine, and pyrimidine bases are characteristic of the intercellular contents, it is surmised that cell content leakage had resulted from this treatment. Furthermore, the authors reported that when suspensions of horse and bovine erythrocytes were treated with DC pulses, the turbidity of the suspensions decreased, which they believed resulted from the lysis of the erythrocytes. It was also shown that the treatment lysed protoplasts prepared from M. lysodeikticus, S. ureae, B. subtilis, and B. megaterium.
The prior art discussed above requires that the electric pulses be discharged into an aqueous solution in which bacteria cells are dispersed. It would be preferable to provide a technique for lysing bacteria cells that enables the cells to be concentrated and lysed in either a moist or dry environment. Further, it would be desirable to lyse substantially all of the spores exposed to the lysing medium, to improve the yield of cell-nuclear material for purposes of identification and analyses. Moreover, while the prior art teaches that an electric field can be employed to puncture bacterial cell surface membranes, it does not appear to indicate that an electric field is capable of lysing bacterial spore surface membranes. Clearly, it is desirable that any new technique usable for lysing should be capable of cleaving bacterial spores as well as bacterial cells.
One of the more important applications of technology requiring the lysing of bacterial cells and/or spores is in facilitating identification of biological agents that are used during bacteriological warfare or in attacks by terrorists. In order to permit known harmful bacteria to be identified, it is important that the DNA and RNA comprising the bacterial cells or spores found in the suspect environment be made available for analysis. By providing a reliable and portable apparatus for lysing bacteria cells or spores collected from the environment, it will be possible to identify bacteriological warfare agents in the field so that appropriate counteractive and protective measures can be implemented. A portable field monitoring device that includes the capability to collect, concentrate, lyse, and identify bacteriological warfare agents will greatly enhance the ability of civilian populations and troops to survive such attacks.